In the processing of photographic elements, especially color film and prints, there is a critical relationship between the temperature of the active solution and the length of time that the sensitized surface is in activated contact with the developer solution.
Thus, if the solution is maintained at a constant, predetermined temperature, there is a specific time interval during which a thorough activated contact should be maintained in order to produce optimum results. Any change in solution temperature will affect the required time of chemical contact. If the solution temperature changes or fluctuates during the period this takes place, it is usually not possible to predict in advance how the time or reaction must be altered to obtain the desired results.
Another factor which should be mentioned has to do with obtaining a uniform chemical action over the entire surface of the area being reacted. As the reaction proceeds, salts are produced which, if they remain in the immediate area, tend to inhibit locally the continuation of the reaction. By producing a uniform agitation of the solution over the whole surface of the areas being treated, it is possible to avoid non-uniform development.
The solutions customarily employed in the chemical processing of exposed photographic film and prints, especially those involved in color photography, are generally very reactive and sensitive to oxidation. When exposed to air for any significant length of time, the solution will deteriorate very rapidly due to the oxidation effect of atmospheric oxygen. In the use of such chemicals, it is therefore highly desirable to limit their exposure to air.
Heretofore, systems and apparatus employed in the development of photographic elements such as films and prints, especially color sensitive elements, have attempted to satisfy the stringent requirements described above by compromising the various factors. Thus, in one system currently in use, a drum is preheated with water to a predetermined temperature. The unit to be processed is then inserted followed by the addition of preheated solution. The print is rotated in the drum. No provision is made to maintain the temperature of the solution and while there is some solution agitation due to the rotation, there is no provision to insure the uniform and optimum velocities of the solution along the surface areas undergoing chemical treatment.
In another arrangement in use, the photographic element is placed in a tray containing solution preheated and maintained at the desired temperature. Agitation is accomplished by shaking the element and/or the tray. Due to the large solution surface exposed to the air, there is rapid deterioration of the chemical plus a tendency to produce a non-uniform distribution of temperatures throughout. Also, in such systems shear forces between the plate and the solution are too small and non uniform to be beneficial.
In a typical commercial configuration, there is provided a termostatically controlled tank of solution into which baskets containing the photographic elements are immersed. Agitation may be accomplished by shaking the baskets or providing agitators for the solution. There are, of course, more sophisticated commercial arrangements designed to meet all of the requirements described above, but they are hardly suitable for the hobbyist or home user or others who do not have the production to justify the investment which is required.
In the arrangements described above, it is seen that it is not possible to meet, on an economic or convenience basis, all of the requirements which would insure quality and reproducible results without resorting to trial and error techniques, at best, for the hobbyist or individual worker for whom a substantial capital investment would be out of the question.